Ground trainer for aircraft personnel



June 12, 1951 Flled Nov 16, 1945 A 77`ORNE V '2 Sheets-Sheot 2 H. A.GlRouD GROUND TRAINER FOR AIRCRAFT PERSONNEL.

tg Sol Ulli! (5.1 u 06 Q\l SS @Sol R June 12, 1951 F'iled Nov. 16, 1945'Patented June 12, 1951 GROUND TRAINER FOR AIRCRAFT PERSONNEL Henry A.Giroud, New York, N. Y., assignor to Bell Telephone LaboratoriesIncorporated, New York, N. Y., a corporation of-New York ApplicationVNovember 16, 1945, Serial No. 629,164

13 Claims.

This invention relatesr to a ground trainer for aircraft and moreparticularlyv to the simulation of the operation of the accelerometeryof an airplane in responseY to ight operations.

The accelerometer of an airplane indicates only accelerations along theVvertical axis of the air.- plane. The instrument does not indicatechanges in velocity which takeplace in a line coinciding withthehorizontal axes of the airplane.

The force along the vertical axis of the airplane is the product of themassv times the component of Aaccelerationalong said vertical axis.(F=ma) and, since the massof a loaded Vairplane may be consideredsubstantially constant in any flight, the forces acting on the airplanemay be expressed in terms of the accelerationsaffecting it. Inmaneuvering an airplane the largestchanges inthe accelerations affectingit are in the direction of its vertical axis. There is, in consequence,

the greatest danger of exceeding the allowable stresses throughexcessive accelerations inthe vertical axis direction.

At restA and. in normal level flight, the force along the .vertical axisof the airplane isdueto its weight. Under such conditions` the airplaneis unaccelerated. However, the accelerometer indicates the force due tothe mass ofthe acceleration responsive element of the instrument. For

simplicity this force will be called the force due to gravitationalacceleration. It is convenient to consider the magnitudes of all theother forces actingon the airplane in terms of multiples of the forcedue to the normal gravitational acceleration which is called. the vgunit of acceleration.

are given in the operating `diagrams for that airplane The visualaccelerometer is used by the pilot'so that he may become familiar withthe accelerations along the vertical axis characteristicofthe airplanein various maneuvers so that maneuvers which would' impose Aexcessiveloads on'the'airpla-nel will `not be; executed. AcceleraticnsY along"thevertical axis` also' are the'v ones having the greatest physicaleffects on the pilot: too great an acceleration causing the pilot toblack out.

The indications ofthe accelerometer also serve to show the accelerationsimposed on an airplane by gusts and rough air in otherwise level flight.Thus it serves as an index to some of the stresses encountered undernormal operating conditions.

In general, an accelerometer consists of a mass suspended for movementagainst the restraints of one or more calibrated springs. The weight ofthe mass is statically balanced by the tension of the spring or springs.A change in the acceleration acting on the mass causes it to movechanging the tension of the spring or springs until the spring tensiononce more balances the force imposed (equal to the mass times theacceleration). The movement of the mass is communicated to a pointerorhand which, when the airplane is in level flight, indicates anacceleration of -l-lg or a load on the airplane equal to the pull ofgravity. The instrument may be calibrated to indicate a range which isfrom -5g to +129. The instrument is mounted in the airplane sov that themass moves in a plane parallel to the vertical axis of theY airplane.

One form of instrument in general use comprises a mass slidable alongtwo vertically7 disposed guide rods, the movement of the mass beingcommunicated to the shaft on which the indicating hand of the instrumentis mounted by a cord which is secured to the upper end of the mass,extends over an upper idler pulley is then wrapped around a drivingpulley secured to the shaft, then extends around a lower idler pulleyand is secured to the lower end of the mass. For restraining themovement of the mass, a helical spring surrounds the shafthaving one ofits ends secured to the shaft and the other of `its ends attached to thecasing of the instrument. When the vertical acceleration of the airplanechanges the mass moves againstthe restraint of the helical spring andthrough the cord, converts its vertical movement into a rotary movementof the shaft. Normally the tension of the spring is such that the massis held in a position such that, through he cord, the indicating hand ispositioned toindicate an acceleration of -l-lg.

Most accelerometers have a maximum reading hand mounted on a hollowshaft surrounding the main shaft and driven from the main shaft by apawl and ratchet mechanism when the main shaft is moved in a directionrepresentative of a positive increase in acceleration. This hand movessimultaneously with the main or continuous reading hand upto Vthe pointof the highest +g reading. Then as the continuous reading hand returnsto indicating Whatever forces are currently being exerted on theairplane, the

maximum reading hand is stopped at the high- Y est indication to whichit has been moved and retained by a retaining pawl which may bedisengaged from the ratchel Wheel to permit the maximum reading hand tobe returned to normal by a suitable hair spring. Thus on any night the"maximum reading hand may be used to indicate the maximum plus value of gor the highest load factor imposed on the airplane. Some instru mentsare also provided with a third or minimum reading hand which issimilarly positioned when the continuous reading hand is movedtopositions indicative of minus values of g.

As an example of the operation of an accela standard type ofaccelerometer is modined by the removal of the movable mass, the drivingconnection therefrom to the shaft from which the instrument hands aredriven, by the removal of the restraining spring or springs and by theconnection of the rotor shaft of `a synchro-re ceiver or so-called"autosyn to the driving shaft of the instrument. For driving thesynchro-re-V ceiver it is electrically connected with a similarsynchro-transmitter the rotor of which is driven from an accelerometermotor unit.

The accelerometer motor unit is controlled by potentials representingthe forces acting in the erometer on a typical night maneuver, when theairplane is climbing the accelerometer hand Will indicate, for example,|2g until, when a suitable altitude is reached and the night is leveledon, the instrument reading will become the normal or -l-lg. Should theairplane be nosed over to start a dive the accelerometer hand passesthrough zero g and goes to some value of -g as the angle of the divebecomes steeper. 'I'he hand Will then swing back through zero g to |12gWhere it remains as the airplane inclines downward. When theYpilotrnoses up sharply to stop the dive the greatest load on the wingsis produced as Will be-indicated by'a reading for example-of +49. Duringthe pull out from the dive the accelerometer hand will indicatediminished values of -g until when the airplane` levels offV the hand ofthe instrument returns to the normalY level night indication of +1g.

VIt is desirable in a ground trainer for an airplane which is equippedwith an accelerometer to give a student pilot-training in the use of theaccelerometer under night conditions which he would encounter in nyingan actual plane which the trainer simulates. To this end it is an objectof the invention to simulate in a ground trainer the functioning of anaccelerometer in response to the simulated maneuvering ofv an airplane.

.It is a-further object of the invention to pro-V vide in a groundtrainer electrically controlled means for operating an accelerometerwhich means are responsive to the operation of the Ystick and enginecontrols of the trainer in simulation of the maneuvering of an airplanein Y night.

;sitions representative of different flight conditions such as, forexample, indicated air speed, angle of attack, altitude, Wing napsposition, accelerometer, etc. Some of these motor units in addition todriving potentiometers and variable transformers from their shafts whichenter into the control of other motorV units of the trainer,

also control the setting of instruments mounted on instrument panels ofthe trainer and duplicate instruments mounted on instrument panels at aninstructors desk. A trainer in which the 1, circuits and apparatusresponsive to the flight controls Y are completely illustrated isdisclosed in the application of E. J. Fogarty and lR. O. Rippere SerialNo. 622,068, nled October 12, V1945.

.-To operate the accelerometer in the trainer,

direction of the vertical axis of the airplane which the trainersimulates. Since it is usual, as previously stated, to consider themagnitude of ac-v Acelerations acting on an airplane in terms ofmultiples of the normal gravitational acceleration, the load supportedby the Wings (lift) in any maneuver is the product of the weight of theairplane by the accelerometer indication or accelerationzlift/Weight oWW Y I Where CL is the coefficient of the lift of the Wings, Viz is thesquare of the indicated air speed, W is the Weight of the airplane andK1 is a constant determinedk by the division of the constant K by W.

In the trainer the term CL, which of the angle of attack and theposition of the wing naps, is determined by the movement of the sliderof a potentiometer driven by the angle of attack motor unit, the termVi2is determined by the movement of the sliders of variable trans-kformers or variacs driven by the indicated air` speed motor unit and thelift is also'innuenced in accordance with the simulated position of theWing naps as represented bythe position of the slider of a potentiometerdriven by the wing naps motor unit. In addition, a nxed potential issupplied Which represents the gravitationalV force whenV the night isassumed to be on the ground.

With an on-the-ground flight condition simu-V lated by the trainer, apotential of phase p1 is applied to the control conductor of theaccelei'-, ometer motor unit of suincient value to cause the shaft ofsuch unitto be rotated to a position representative of a normal or -l-lgposition of the hands of the accelercmeter resulting in the set- Y inthe throttle opening causes the control of an R. P. M. motor unit tooperate its shaft through Vpositions representative of an increasingsimu- V lated engine speed thereby operating a poteneffective to derivea controlling potential whichV is modined by potentiometers and variacsdriven by the shaft of the indicated air speed motor unit and furthermodined by potentiometers and variacs driven by the shaft of the thrustmotor unit, to operate the motor of an angle of attack motor unit. Themotor of the angle of attack unit isalso controlled by aV potentialwhichis is a functionv 53. varied in-r accordancefwltlrithe'fsimulatedposition. oti'wingFllapssasEdeterminedbyfthe settinggof thef shaft'oamotor unitin4 response-'topthe-operation i of ai simulated: winggrflapsfcontrol. In `response to Vthese controlV potentials, the; motor. of 5the'angle'of attackI unit -is operated to position its shaft intola-fpositioni vrepresentative of' the-simulatedfangle of attack'f Theoperations of theindicated airrspeed and-'anglefof attacki motor unitslareieffectiveto control axmotorfunit whosershaft isdriven-'representativen of 'theiangle oft climb of f thesimulated'flight. Thevshaft of 'the'zangleof climbmotor unit drivespotentiometers: which aree'efiectiveto"control theraltimeterfmotor unit.

Theshaft offths latter zunitxisfthusfoperated -rep-v r'esentative' of`Athe altitude1attainedin thef simulated flight. If the'angle-:of'attacknincreases to a greater positive value a. rpotentiometercontrolled byfthe'fangle of attackzmotor-t unit is. effective "toappiya'lphase pl potential to thezcontrol conduc- .20

tor of the accelerometerl motor;unit. Thisl potrential'isl Varied underthecontrol of'. tandemconnected variacs driven bythe `shaft ofthe-indicated; air speed motor unit so that-thepotential applied to theAcontrol conductor'of-theacceler- 25 If.l the angle of attaclcchangesxtofanegativey value,A theangleof attack potentiometer iseffective to apply afphase .e2 potential tothe control conductor-'of theaccelerometer motor unit which will be instrumental ini-causing'thelaccelerometer motor unit to operatethe-hands'oftheaccelerom- 40 eters'ina directionY representative of a negative valueof vertical acceleration:This potential is modified in accordance'with the; square of theiindicated nair speed by other vtandem-connected.

variacs driven by the-shaft-oflthefindioated air 45 speed .motor `unitSince thepositionof the-:wingflapsrof an air-v plane will also influencethe lift of the airplane rr=flight`and will increa'seftheelift as theyare movedr from their-up to their. down positions,4 thisf lit .effect onthe operationofithe accelerometers is-fsimulated inA the'trainer.byfazpotential of phase qrl'wlflich` is varied by theE variacs driven bytheY` indicated air speed motor Vunit inaccordance lwith the-.squarefofthe indicated-airspeed, and which potential is increased byf'aVpotentiometer'driven from the shaft of the wingflaps motorunit'. Thisvpotential will cause the motorof the accelerometermotor unit to drivethe-accelerometer hands inza direction' representative. of a-:positivevalue 60 of vertical acceleration.

vSince theY accelerometerfunctions: when the airplane isdn-flight, thepotentials of'phase 01A and. phase p2 derived.bytheindicated air speedvariacs, asrpreviously described, are.'effectiveonlyL 65` when ail-ightis simulated; This isv accomplished by a relay which is operated onlywhen the-shaft of-.the indicated fair speed/motor unit has moved from.its zero` air speed position andiv which .relay wheny operatedappliesphaseqD-l and phase-m2 po- 70' tentialsto the-tandem connectedindicatedy air speed variacv previously referred'to.=

It the. angle of attack` is increased rto such a value as Wouldfin an'actual-airplane cause a stall conditiona and loss ofli-ft, astallrelay. isoperated l '15.-

This phase 30 potentiometer and wing-flaps potentiometer, from thecontrol conductor of the accelerometer motor unit and applies phase v,olpotential to such control conductor 'of a Value determined by the squareof the indicated airl speed. This potential is of less value than thesum of the'phase o1 potentials applied to the control conductor prior tothesimulation of the stall condition and therefore the accelerometermotor unit is operable to cause the accelerometers to show reducedpositive readings.

During a simulated flight the phase o1 and phase p2 potentials derivedat the indicated air speed variacs and selectively applied to thecontroll conductor of theaccelerometer motor unit in accordance-with thesetting of the slider of the ange of attack potentiometer, and the phasep1 potential vapplied under the control of the wing flaps potentiometer,are made effective by the operation of first and second flight relayswhich operate as soon as the'shaft of the altimeter motor unit movesfrom its Zero altitude position. One of these relays upon operating isalso effective to render the application of the normally applied phaseo1 potential to the control conductor of the accelerometer motor unitineiective during flight` latter relayreleases at once'to render thispotential again effective and the other flight relay which is renderedslow to release maintains phase pl potential of values determined by theindicated air speed'variacs andV by the angle of attackl and Wingflapspotentiometers applied to the control conductor; These-phase (plpotentials are thus additive until the second flight relay releases tocause amomentary positive increase in the readings of the accelerometersrepresentative of the;

jolt delivered to the accelerometers due to landing.

The features of the trainer by which the foregoing control of theaccelerometers is accomplished having been briefly described referencemay now be had, for a more comprehensive understanding of the invention,to the following detailed descriptionr when read in connection with theaccompanying drawings in which:

Fig. 1 shows above the dot-dash line the accelerometer motor unit, showsin the boxes in the right portion of the figure the schematic`representationV of the accelerometers on the pilots instrument paneland` on the instrument panel at the nstructors desk, and in the lowerleftpor'-v tion of the'figure a schematic representation of a portion ofthefangleof attack motor unit; and

Fig. 2 shows in the lower right portion thereof a.I potentiometer drivenby the angle of attack motor unit of Fig. 1, in the lower left portionthereof the schematic representation of Ysuch portionsfof the indicatedair speed motor unit as are necessary for'an understanding of thepresent invention, in the upper left portion thereof a schematicrepresentation of such portions'of the altimeter motorv unit as areconcerned with the present invention andV in the upper right portionthereof 'the schematic representation of such por'- tions of-thewingflaps motor unit as are concerned with the present invention.

For a complete-disclosure of the invention Fig. l'should be positionedto` the right of Fig.. 2..

Theaccelerometer motor unitdisclosed in theA upper portion of Fig.. 1isof the .type disclosed and fully describedin Patent No. 2,428,767granted t0 Albert-Davis-Gumley-Holden onOctober 14, 1947;

When, however, a landing is made'theV It includes a ldirect currentreversible type'motor b IIE. whose stator winding is energized by directcurrent from the -I-lSO-volt bus bar |30 through the lamp resistance I8under the control of the RVi reversing relay ||1, which relay is in turnunder the control of the plate relay ||5 associated With the gas-iilledYtube |05. The rotor Winding of the motor is energized by positiveimpulses of current transmitted therethrough by the firing of thegas-filled tube |04. The motor, through the reduction gear box |20,rotates the shaft |2| which shaft, through gears |22 and I 23, turns theslider of the balancing potentiometer ACLI and through gears |24 Yand|25 turns the rotor of the synchro-transmitter |20.

In general the circuit for controlling the motor IIS comprises a dualtriodeamplier tube which receives a signal incoming on signal controlVconductor |0|, amplies it, and applies 'it through the' step-uptransformer |02 to the plates of the dual diode rectifier tube |03. Thetube |03 serves as a full wave rectifier to rectify the output signalfrom the tube |00 and to apply it as a positive potential to the grid ofthe gas-nlled tube |04. The output potential from tube |00 is alsoapplied through the upper secondary winding of transformer |02 to thecontrol grid of the gas-lled tube |05. Direct current for providing gridbiases to the control grids of tubes |04 and is supplied from the rightsecondary winding of power transformerA |00 through the dual dioderectifier tube |01 under the control of the grid bias control rheostats|00 and |09. Filament heating current for all the tubes is supplied fromthe other secondary windings of the power transformer |00, the primarywinding of which is energized from the 115-volt Vbus bar I0. Platepotential is supplied to the plates of the amplifier tube |00 overconductor from the y+130- volt bus .bar |30 and 60-cycle plate potentialis applied from the ll5volt phase o1 bus bar ||9 over conductor |2 andchoke coil |40 to the plate of tube |04 and through resistance lamp ||3and thence in parallel through resistance I4 and the winding of the RVrelay ||5 and choke coil |4|` to the plate of tube |05. The RV relay ||5in addition to controlling the circuit of the RVI relay ||1 establishesover its lower contacts a short circuit of the resistance in series withthe biasing circuit of tube |05 to increase the positive bias of suchtube thereby insuring that relay l5 will be held operated so long astube |05 continues to'conduct in response to an incoming signalpotential.

The jack |42 is provided to enable the motor control circuit to betested for correct operation.

To prevent the motor l0 from rotating the shaft 2| to such a positionthat the slider of potentiometer ACLI might be driven off either end ofthe potentiometer winding, the limit switches Ll and L2 are providedeither of which when operated opens the stator circuit of the motor ||6and closes the circuit of relay LS which upon operating opens the rotorcircuit of the motor to arrest further rotation of the motor.

When the input signalv potential applied tov transmission of an impulsethrough 'the rotor circuit of the 'motor H6' each time the tube |04fires on each positive half wave oftherplate potential and the motorwill'run in one direction.

In response to an input signal-which is out of phase with the potentialapplied to the plate of tube |05, tube `|05fwil1 not conduct andconse-VV quently relays |'|5 and ||1 will not operate but,y

since tube |04 will fire on each positive half wave4 of the potentialapplied to its plate, the motor IIB will be operated in response to theincoming signal in the reverse direction of rotation.

The altimeter, indicatedv air speed, anglel of 1 attack, andrwing flapsmotor units shown schematically in Figs. 1 and 2 are similar to theaccelerometer motor unit but to avoid increasingV the disclosureunnecessarily they have been abbreviated to show only theinput circuitsof the rst amplier tubes thereof, to show the RV, RV| and LS relayswhich control the circuits of the motors and to show the motor reductiongear" boxes and limit switches.

To prepare the trainer for the simulation of a night, the enginecontrols are operated to cause the simulation :of the operation of theengineY resulting in the simulated development of thrust Y will bedeveloped and the shaft 200 of the indi-- cated air speed motor unitwill be in a position representative of zero air speed in which positionthe L| limit switch 20| will be operated to the alternate position andthe AS relay 202 will be unoperated. With V*relay 202 unoperated thewinding of the indicated air speed variac IAI will be connected into acircuit extending from ground therethrough and over the lower VbackAcontact of relay v202 to ground through resistor 203 and the winding ofthe indicated' air speed variac IA1 will be connected into a circuitextending from ground therethrough and over the inner lower back contactof relay 202 to ground through Y resistor 204 to discharge the windingsof the variacs.

At this time the shaft 205 ofthe altimeter` motor unit will be in aposition representative of' zero altitude in which positionlthe L| andL3 limit switches 200 and 201 will be operated to theiralternatepositions in which a circuit is estab-V lished from ground over thealternate contacts of such switches and through the winding of the GRDrelay 208 to battery and ground. Relay 203 is thus operated and remainsoperated until the limit swtich 201 releases when the simulated flightbecomes airborne.Y So long asvrelay 208 remains Voperated the F and FIflight relays 209 and 2|0 cannot operate.

At thistimeY the shaft |21 of the angie` of attack motor unit will be ina position representative of about a `z-l-8-'degree angle of attack'suchas wouldv be the case with all of the landing gear wheels on the groundor night deck of a carrier.

When the simulation of the removal of the wheel chocks has been made apotential is applied to the control conductor 2|| of the indicated airspeed motor unit of a phase which causesrthe motor 2|2 of such unit toturn shaft 200 in a` direction representative of the development of airspeed as the s imulatedI flight moves over thev4 ground. As soonas'indicated airspeedY is develnped', :shaft-20 I permits. the 'LI limitYswitch. to restorezthereby establishing the obvious circuit i--forftheAsrelay. 232 which. thereupon operates, opening the =dischargecircuitsofthe variacs IAI ...andfIAIsand connecting. thewinding of variac ll'iIAIIr over 'the lower front contact of relay=202pto '-bus bari 2 I 3to which 40-volt phasenl lpotential vis applied, and connecting the.winding of variac IA'Lvover the innerlower front contact of relay 'fromthe No. 2 terminals toward the No. 4 termi- 15 -nalsiof theirwindings asthe simulated indicated airfspeed increasesgincreasing potentials-ofphase v#1p1-fand'phaseipZ' are-derived-'at such sliders and appliedthrough the windingsof variacs IA2 and "IAB, respectively. Thesliders-of the la-tterfvariacs .20

are 'also-driven `through the gears 2|8,2|9 and 22 Il incorrespondencewiththe -movement -ofthe "sliders of va-riacs IAI and IAL-ahd potentialsof phase p1` and phase. p2 are `thereforederived at tors'22I and'2'22.Since the-variacs IAI and IAZ f' are connected in tandem, the potentialof phase qui applied to conductor22| will vary in accorci- 'ancewith theysquare of 'the' simulated indicated 'air speed and sinlilarly Sincethe-variacs IAI and t'30 ,IA8`are connected in tandem 'the potential offphase` :p2 applied vtoY conductor-222 will also Vary in accordance withthe square of the simulated iairspeed. These derivedpotentials'however,are

not eiective until an airborne orvlight condition 35.

issimulated andthe'jF and FI relays-209 and 2li) "become operated.`

Until the F relay 209 operates, potential of phase p1 is applied throughresistor 223 to control conductor IDI of the accelerometermotorunits*140 `This; potential ofA phase el applied to conductor 45 IDI issuch as to cause the motor |I6 of the accelerometer motor unit to rotateshaft-12| in a A`direction representative of aY positive increase in the4vertical acceleration. /As kthe Shaft rotates "the slider offbalancingpotentiometer ACLI is driven by the: gears |22 and |23 toward theaNo.' 3`terminal of its winding. -This winding has its i'No; 1 :terminalconnected Ythrougha resistor |728 of r2200 ohms to the phase p1-bus bar2|3 and has litsifNofSterminalcOnnected through a resistor "|29 of 1425ohms to the phase q 2b us bar ZIA and )normally lthe-slider ispositioned so thatthe poten- J" tials lof'phase o1 and phase o2, whichare'180 degrees out lof phase, appliedthereto at its point of engagementwith the windingwill be balanced.

In this position `the vshaft |2I, Vthrough theY gears v'I-24 and|25,will have rotated the rotor of -syn- `chip-transmitter r|26 to aposition inwhch the l'synchro-receivers I3| and- I 32 controlledthere-"by are operatedintd positions in which the inv'dicating hands VI33and|34 of the accelerometers -|35and |36 at lthe-pilots pedestal and atythe 'instructors desk Will'indicate 0g.

",As the sliderofy potentiometer ACLI moves totothe application ofpotential of phase A p1 to conftiol-conductor I-|1I an increasinglpreponderance of potential ofphasep2 will appear on the slider and willbe yappliedthroughresistor 13,1 to control conductor |0I untilVthispotential-balances the 75 potential .of phase. (p1. appliedwtosuchconductor. .The motor I I6 :will thenstop. v:Themovementoi the rotoroi.synchro.transmitter |26 through .the rotation of.shaft.I2I.willonowfhave controlled the synchro-receivers. |3I.and |32 to set thevhands |33 and- |34 :of the. accelerometers |35. and |36 to indicatethenormal*ffgravitational acceleration of. +19.

`Wl'ien sulicient indicatedair speedhas-.been attained.- enough..simulated :lift 1 Will be developed Ato-represent' an airborne condition`of'ilight` As .soon as thiscondition is simulated the shaft-205 of thealtimeter motor unit will rotate insucha direction as to .reelaseftheLI-.and L3 Iimit switches r2EiB.and.-2'l thereby releasing. the GRDrelay 208 and .permittingA the F andy FI night relays 209 and 2| G..to-operate. 'Withfthese relaysoperated conductor 22| iszconnected .overthe contacts of Irelay- 2 I0 *through ythe-potential .divider compris-.ing resistorsfEZG. and 22lto ground and inparallel .therewith throughthe y.upper "I5y -per centpf .the v.windingvothe. angle-,of attackpotentiometer 4AAB .to ground. #Conductor 222 is also connected overAthe inner upperl front Acontact of relay-,209, their slidersrespectively and applied to Aconduc- 25.

through: resistor.' 228, and.. through the 1ower..25

, percent .o f, thenwindingof potentiometer. AA8 :to fgiound. Theang-leofA attack. at .the time of simu- .lated .takeeoit will Joe..positivevand .consequently theslider of potentiometer willibepositioned between: the; srolmdtan, andthe .151023, .termina ...or the.ynot-.entiometer .winding and. apotentialpf phase p11-willbeappliediromsuch, 1idr...0,ver thcupper. `back .Contacter the, stall S.S 1telay.2.29

.,andpthroush. resistor 230- .,t0.:.cQntr,01 conductor ,Il l- Of theaecelerorneterrnotorjunit. This potential-will thereforezvary as,theisiuare of the 1in- @ligatedair1 soetwas .daterminedby the .varietes4,the lower backvcontact of theS relay 2T29,.throi.igh resistor 23| andthroughthe winding 4of ,thawing aps potentiometer ['WFII .for.energizing v,such winding. ,.But-,. with .thawing tflaps assumedto ,lbein the` up, position representedby the yposition of.. shaft 2320ithewingflaps motor unit'and the position of theslider ofthepotentiometer. WFG

andthrough resistor 223 to control conductor I IJI and the phase 1p1potential normally applied through -resistor2v23 to control 'theaccelerometer `ifnotor--unitV to set'the hands vof accelerometers |35and |-36,"to`-their -f-lg positions is-no vlonger effective. Howeven-theAphase :el potential applied lthrough resistor iZlILis now effectiveandas the student `pilot moves" back the stick ofthe trainer' to execute vaclimbing maneuver, andthe angle Yof `attack Vvconsequently increases,theY phase pl potential applie'd-fthrough resistor- 23|) increases-dueto the `movement of the sliderof potentiometer AA8v toward Vthe-1Tof3terminal of 4its winding and -iurther increases in accordance -withthersquare of the indicated air speedasthe :ward the'No'; Sterminalofits Winding in response 70v Y l sha-ft jI2I-inadirection:representative of an `increasein the vertical*accelerationuntil the'slider Voi? balancing potentiometer ACLI has been movedsuiiicientlyv toward` the ,1.1. No. 3v terminal of its winding toapplya'phase p2 potential to control conductor ||l| which balances the phasep1 potential Vapplied thereto through resistor 230 whereupon the motorwill stop. As the result of the rotation of shaft |2| thesynchro-transmitter |26 is operated to drive the synchro-receivers |3|and |32 in a direction representative of an increase in accelerationwhich will be indicated by the accelerometers |35 and |36. It Will beassumed that Vfor the simulated climbing maneuver theaccelerometers-will indicate a vertical acceleration of, for example,+2g.

When the simulated flight has attained a desiredaltit'udethe studentpilot pushes back on the stick thereby causing a, reduction in the angleof vattack and the leveling off of the night. The .reduction in theangle of attack causes a reducl tion in the phase .1p1 potential appliedthrough resistor 23to control conductor IUI. The potential of phase p2now applied to conductor z from the slider of the balancingpotentiometer ACLI of the accelerometer motor unit will be greater thanthe potential of phase p1 and as a consequence thev motor I|6 will beoperated to drive the shaft |2| in a direction representative of Vareduction in acceleration. The rotation of the shaft |2| will now movethe slider of potentiometer ACLI back toward the No.Y 1 terminal of itswinding thereby reducing the phase p2 potential applied from such sliderto control conductor lill' until it balances the phase p1 poten- Vtialwhereupon theV motor-will stop. Through this movement of shaft |2| thesynchro-transmitter |26 is operated and through the synchroreceivers 13|and `|132 driven thereby the accelerometers |35 and |36 are adjusted toshow a reduction in vertical acceleration to the level flight readingsof +1g.

It will now be assumed that the student pilot -pushes the stickvYforward to simulate a nosing down `of the simulated flight. In responseto this operation of the stick the angle of attack is changed from apositive to a negative value and the slider of the angle of attackpotentiometer rAAS] is moved to a position between the ground tap andthe No. 1 terminal of its Winding. The

Vpotential now applied from the slider of such vpotentiometer over theupper back Vcontact of relay 229, through resistor 230, to controlconductor '10| of the accelerometer motor unit V,changes from phase p1to phase o2, the value of which phase p2 potential increasesas the anglei of attack increases in a negative direction and n the shaft |2| in adirection representative of a change from a positive to a negative valueof acceleration. As the shaft |2| rotates the slider of balancingVpotentiometer ACLI` is moved towards the No. 1 terminal of its windinguntil a potential of phase p1 is applied from the slider to controlconductor IUI which balances the `phase p2 potential applied to suchconductor through resistor 230 whereupon the motor will stop. Throughthe movement of shaft I 2|, the synchro-transmitter |26 is operated and,

` through the synchro-receivers |3| and |32 driven thereby, the hands|33V andl |34' of they accel- Herometers |35 and |36 are Ymoved in acounterclockwise direction through theirV zero Vpositions to -gpositions as, for example, to -lgi value and with the slider oi theangle of Vattack potentiometer AA8 now positioned on Vthe N053 terminalside of the ground tap, `the potential applied from such slider becomesof phase pl and increases as the indicated air speed ofthe diveincreases. This potential applied to control conductor |0I of theaccelerometer motor unit causes the motor thereof to rotate shaft I2| toa position representative of a change from Vanegative value of g to-apositive value of y as will be indicated by the hands |33Yand |34 oftheaccelerometers |35 and |36. kIt will be assumed that as'the `speed ofthe dive increases the Yaccelerometers become set to indicate anacceleration of, for example, 1/ggn When the pilot pulls back on thestick to cause a sharp nosing up of the flight to stop the dive, theangle of attack is increased in a positive vdi rection whereupon theslider of potentiometer AA8 is moved further toward the No. 3 ter-Yminal of its winding thereby increasing the'potential of phase o1applied through resistor 230 to control conductor |0I and controllingthe motor H6 of the accelerometer motor unit to rotate shaft |2| in adirection representative of an increase in verticall acceleration. Underthis condition of nosing up out of a power dive the greatest load on anairplaneV is produced. In the trainer this will appear as a markedincrease in the +g settings of the hands of the accelerometers |35 and|36 as the shaftV |2| 'is rotated. It will be assumed that for the simu.

lated dive the accelerometers will show readings of +4g at the time ofthe pull out.

As the flight noses up after the pull out, the

indicated air speed drops andthe value of the V phase p1 potentialapplied from the slider of angle of attack potentiometer AA8 decreasesWhereupon'the preponderance of phase p2 potential applied to controlconductor I 0| from the slider of the balancing potentiometer ACLI ofthe accelerometer motor unit is eiective 4to cause the shaft |2| to berotated in a direction representative of a gradual decrease in verticalY acceleration from the maximum reading of +4g i to the normal leveliiight reading of +1g when the pilot again levels the flight off.

If in the simulation of a climbing maneuver the angle of attack isincreased to the maximum or about +15 degrees, the L2 limit switch'l38driven bythe shaftV |2`| 'of the angle or attack motor unit will bemoved toits alternate position thereby establishing a circuit fromground, over the contacts of such switch, over conductor |39 and tobattery and ground through the winding of the stall (S) relay 229. Withthis relay operated, the phase p1 potential applied over its throughresistor Y23|] to control conductor IUI.

This potential is of less value than the potential previously appliedand causes the acceleromtact of relay-223over-Whichlphase p1 potentialmovement of the` w-ingnapsfto theiridownl position, in which positionthais'liderfotthev wing lflaps potentiometer-WF4lwillfbe'attthefNo.y 13terminal of its winding. -Withltheslider ofthe Wing naps vpotentiometerWF# so lipositioned, VLpotential .of phase p1 isappliedi'to-control'conductor IUI 'of the accelerometer-motori unitvthrough resistor 233, which potential vwill'varyasrthea-square of theindicated air speedas'dtermined by. the indicated air speed *variacsIAl..1;andlIA2. Atthe same time potential-oflphasewpl is-also applied tocontrol conductor l-'UI 'f-'thiough resistor 230 which varies as the'yangle ot'attackas determined by the angle ofatta'ckpotentiometerAA-and-as the square of theindioated-air speed as determined by thevaria'csfIAIHandIAL -The sum of these potentials, however,=duetofthereduced indicated air speedfwill'besuc'has-tocause the accelerometermotorunitto' hold'the readings of the acceleromete'rs atabout -{-'1g.

As soon as the altimete'r reading reaches zero the Ll and L3limit-switche'sl'ZB'and 201 'of the altimeter motor funitoperate-'totheir alternate positions theiebyfcausing-the reoperation of 'the GRDrelay 2D8 andthe releasev of the Fand FI relays'209 and 12N.lRelay'QOSifupon releasing again renders the application Yi?` phasefpl'potential effective from thelpoteiitial-y divider comprisingresistors 224andl225,lthrlough resistor 223. to control conductor l I,andrelay`32 l 0whichlis slow to release maintains the` application ofphase p1 make a quick -movem'entfinfadirection representative lof anincreasefin'ver-ticalacceleration which is indicated by increasedreadingsofthe accelerometers. `As --soon f as relay f 21 D releases Ythis augmented -potential of phase qply is reducedi to the potentialapplied through resistor 223 or the potential representativeV of thenormal `or gravitational acceleration condition vwhereupon the motorunit isfoperatedunder'the control of the balancing"potentiometerACLI'ftore" turn the shaftl I2lf toi apoisition -representativeof |1gaccelerationlwhichfwill then be indicated by the accelerometers. Thisnu'ctuation of the hands of the accelerometers simulates the increase inreadings-which"wouldv result -from the" jolt of landing. I

The resistor 234 Vof 5,000 ohms resistance Iis connected fromcontrolconductor HH lto ground "thereby placing'at-lowf'resistanceacrossthe 'accelerometermotor unit input morder to reduce *fl'l'4 the effectsof the accelerating forces applied through resistors 223, 230 and 233.

-Whatis claimed is:

l. In an aircraft trainer wherein the night operations of an airplaneare simulated, a source of current, means for deriving a potential fromsaid source commensurate with the simulated gravitational acceleration,meansfor rendering said potential effective when an on-the-groundcondition of night is simulated, a simulated accelerometer, and meansresponsive to vsaid potential for adjusting said accelerometer to show areading of -l-lg representative of the normal.

vertical acceleration due to the gravitational force.

2. In an aircraft trainer wherein the night operations of an airplaneare simulated, a source of current, a control conductor, means forderiving a potential from said source commensurate with the simulatedgravitational acceleration, means for applying said potential to saidconductor when -an on-the-ground condition of night is simulated, abalancing potentiometer for deriving a potential from said sourceopposite in phase to said nrst potential and for applying it to saidconductor, a motor responsive to the summation of the potentials appliedto said conductor for adjusting said potentiometer until the sum of thepotentials applied to said conductor becomes zero, a simulatedaccelerometer operable by said motor to show a reading of -i-lgrepresentative of the normal vertical acceleration due to thegravitational force when said balancing potentiometer has applied apotential to said conductor which balances said nrst potential.

3. In an aircraft trainer wherein the night -operations of an airplanearesimulated, a-source -o current, means for deriving a potential fromsaid source which varies -in accordance withthe square of the simulatedindicated air speed of the simulated night, means for rendering saidpotential effective when an airborne condition of night is simulated,means for modifying said potential` when thus rendered effective inaccordance with the simulated angle of attack of the simulatedL night,said latter potential having a value commensurate with the simulatedgravitational acceleration when the indicated air speed and the angle ofattackare adjusted to simulate a leve. and straight night, a simulatedaccelerometer, and means responsive to said modified potential foradjusting said accelerometer to show a reading of -l-lg representativeof the normal vertical acceleration due to gravitational force.

f 4. In an aircraft trainer wherein the vnight operations of an airplaneare simulated, a source of current, two tandem connected rotaryAtransformers for deriving a nrst potential from said source whichvaries in accordance with the square of the simulated indicated airspeed of the simulated night, a potentiometer for rnodifyincY saidpotential in accordance with the simulated angle of attack of thesimulated night, lmeans operable to simulate an airborne condition ofnight, a relay controlled by said means for rendering said nrstpotential enective, said'modined potential having a valuel commensurate`with vth simulated gravitational acceleration when the v'indicated airspeed and the angle of attackfa're adjusted to simulate a levelandstraight night course, a simulated accelerometer, and means responsiveto said'modined potential for-adjust- -ing said accelerometer to show areading of -l-lg representative of the normal vertical accelera- Vtiondue to gravitational force.

5, Inan aircraft trainer wherein the flight operations of an airplaneare simulated, a source of current, a control conductor, means forderiving a potential from said source which varies in accordance withthesquare of the simulated indicated air speed of the simulated flight,means for rendering said potential applicable to said conductor when anairborne condition of flight is simulated, means for modifying saidderived potential in accordance with the simulated angle ,lo

of attack of the simulated flight, said latter potential having a valuecommensurate with the simulated gravitational acceleration when theindicated air speed and the angle of attack are adjusted Yto simulate alevel and straight flight course, a balancing potentiometer for derivinga potential from said source opposite in phase to said latter potentialand for applying it to Vsaid conductor, a motor responsive to thesummation of the potentials applied to said conductor forv adjustingsaid potentiometer until the sum of the potentials applied to saidconductor becomes zero, and a simulated accelerometer operable by saidmotor to show a reading of +1g representative of the normal verticalacceleration due to gravi-A tational force.

Y 6. In an aircraft traner wherein the flight operations of an airplaneare simulated, means for simulating the indicated air speed of asimulated ight, means for simulating the angle of attack of a simulatedflight, a source of current, means controlled by said air speedsimulating means for deriving potentials of opposite phase from saidsource which vary in accordance with the square of the simulatedindicated air speed of the simu-` lated flight, means controlled by saidangle of attack simulating means for modifying one of said potentials inaccordance with a positive value of/ the simulated angle of attack ofthe ysimulated flight, means controlled by said angle of attacksimulating means for modifying the other of said potentials inaccordance With a negative value of the angle of attack of the simulatedflight, and simulated accelerometer,

and means responsive to said modified potentials '7. In an aircrafttrainer wherein the flight op- 60 erations of an airplane are simulated,a source of current, means for deriving first and second potentials ofopposite phase from said source which vary in accordance with the squareof the simulated indicated air speed of the simulated flight, apotentiometer for modifying the first of said derived potentials inaccordance with a positive value of the simulated angle of attack of thesimulated flight, means for modifying the second of said potentials inaccordance with a negative value of the simulated angle of attack of thesimulated flight, a simulated accelerometer, and means responsive to thefirst modified potential of one phase when the angle of attack is variedfrom a level flight angle over positive values for adjusting saidaccelerometer to show a varying positive value of the simulated verticalacceleration of the simulated flight, and responsive to the modifiedfirst potential of the same phase and then to the modified second po-'l0 tential of the opposite phase when the angle of attack is variedfrom a level flight angle over declining positive values and thereafterover increasing negative values for adjusting said accelerometer toAShow a value 'of simulated ver- 116 tical.acceleration'which variesfrom a norliial -l-lg value throughra zero value to aminus value.

8. In an aircraft trainer wherein the flight operations ofan airplaneAare simulated, a source of current, a control conductor, a rst pair oftandem connected rotary transformers for deriving a first potential ofone phase from said source which varies inaccordance with the square ofthe simulated indicated airspeed of the simulated flight, a second pairof tandem connected rotary transformers for deriving a second potentialopposite in phase to said rst potential which varies in accordance. withthe square of the simulated indicatedair speed of, the simulated flight,means operative when an airborne condition of flightisbeing simulatedfor rendering 4 said potentials: effective, a potentiometer Yformodifying one of said potentials in accordance with a positivevalue andthe other of said potentials in accordance with aV negative value Yofthe simulated! angle of attack of the simulated flight and for applyingsuch modified potential to saidconductor, afbalancing potentiometer forderiving apotential opposite in phase to the modiiied potential appliedto said conductorV and for applying ,it to said conductor, a motorresponsive to the summationof, the potentials applied to said conductorfor adjusting said balancing potentiometer until the sum of thepotentials applied to said conductor becomes zero, and simulatedaccelerometer controlled by said motor to show a varying DQSitivevalueof the simulated vertical acceleration of the simulated flight when theangle of attack is varied from a level iiight angle over positive valuesandV to show a value ofsimulated vertical acceleration which varies froma normal +19 value through a zero value to a minus value when the angleof attack is varied from a level flight angle over declining positivevalues and thereafter over increasing negative values.

9. In an aircraft trainer wherein the flight operations of an airplaneare simulated, a source of current, a control conductor, means forderiving a first and a second potential of opposite Y phases from saidsourcewhich vary in accordance with the square of the Simulatedindicated air speed of the simulated flight, means operative when anairborne condition of flight is being simulated for rendering saidpotentials effective, means for modifying said first potential inaccordance with the simulated position of wing positivenvalueofthesecond of said derived potentials in accordance with a negative value ofthe simulated angle of attack of the simulated flight, means forselectively applying said modied potentials-to said conductor, a motorresponsive to the summation of the potentialsapplied to said conductorwhich are representative of the simulated lift of the simulated flight,and a simulated accelerometer controlled by said motor to show thecurrent value of the simulated vertical acceleration of the simulatedflight as determined by the value of said lift.

10. In an aircraft trainer wherein the flight operations of an airplaneare simulated, a source of current, means for simulating the angle ofattack of a simulated night means operated by said first means forderiving a potential from said source which varies in-accordance withthe simulated value representative Fof the reduced value of lift 17 whena stall condition of flight is simulated, a motor responsive to saidpotential and a simulated accelerometer controlled by said motor to showthe current Value of the simulated vertical acceleration of thesimulated flight as determined by the value of the simulated lift.

11. In an aircraft trainer wherein the flight operations of an airplaneare simulated, a source of current, a control conductor, means forderiving a first and a second potential of opposite phases from saidsource which vary in accordance with the square of the simulatedindicated air speed of the simulated flight, a potentiometer formodifying onef of said derived potentials in accordance with a positivevalue and the other of said derived potentials in accordance with anegative value of the simulated angle of attack of the simulated flight,means for modifying said rst potential in accordance with the simulatedposition of wing flaps, a relay effective when unoperated to enable saidmodified potentials to be selectivel5T applied to said conductor, amotor responsive to the summation of the potentials applied to saidconductor which are representative of the simulated lift of thesimulated flight,

a simulated accelerometer controlled by said motor to show the currentValue of the simulated vertical acceleration of the simulated flight asdetermined by the value of said lift, means for modifying soid rstpotential to produce a poential representative of the reduced lift whena stall condition is simulated, and means for cperating said relay todiscontinue the application of said potentials modified in accordancewith the simulated angle of attack and with the simulated position ofthe wing ilaps to said conductor and to apply said potentialrepresentative of the reduced lift when a stall condition is simulatedto said conductor whereby said accelerometer is controlled to show areduced acceleration due to the stall condition.

12. In an aircraft trainer wherein the flight operations of an airplaneare simulated, a source of current, means for deriving a potential fromsaid source which Varies in accordance with the simulated lift of asimulated airplane, means for deriving a potential from said sourcecommensurate with the simulated normal gravitational force applied tothe simulated airplane, means for momentarily rendering both of saidpotentials effective when the landing of a simulated flight issimulated, a motor responsive to the summation of said potentials, and asimulated ac- -ill celerometer controlled by said motor to show thecurrent value of the simulated vertical acceleration of the simulatedght, said motor causing said accelerometer to show a sudden momentaryincrease in acceleration in response to said latter means representativeof the eifect on the accelerometer due to the jolt of landing.

13. In an aircraft trainer wherein the flight operations of an airplaneare simulated, a source of current, a control conductor, means forderiving a potential from said source which varies in accordance withthe square of the simulated indicated air speed of the simulated flight,a first and a second relay operable in cascade for rendering saidderived potential eiective when an airborne flight condition is beingsimulated, a potentiometer for producing from said derived potential afirst potential which Varies in accordance with the simulated angle ofattack of the simulated flight, means for producing from said derivedpotential a second potential which varies in accordance with thesimulatedv position of wing iiaps, means for deriving a third potentialfrom said source and applying it to said conductor when said first relayis released representative of a landing, a balancing potentiometer forderiving a potential from said source opposite in phase to said otherpotentials and for applying it to said conductor, a motor responsive tothe summation of the potentials applied to said conductor for adjustingsaid balancing potentiometer until the sum of the potentials applied tosaid conductor becomes Zero, and a simulated accelerometer controllableby said motor, said second relay being slow to release following therelease of said iirst relay when a landing is simulated whereby said rstand second potentials are momentarily added to said third potential tomomentarily increase the reading of said accelerometer at the moment oflanding.

HENRY A. GIROUD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,366,603 Dehmel Jan. 2, 19452,395,477 Gumley Feb. 26, 1946 2,406,221 Hornfeck Aug. 20, 19462,475,314 Dehmel July 5, 1949

